Managing local music with Music.app and syncing with Finder iPhone sync still works good for me, but Music.app does seem unmaintained for a couple years now with some annoying bugs since the terrible Big Sur rewrite. Despite the flaws this combination is still the best music library management + mobile sync solution I've seen (plz recommend!), but I feel eventually will have to write a system myself since the software is not maintained and not cross platform.

Part of the issue with the Music “rewrite” is that it’s less of an actual rewrite and more of a copypaste from iTunes. Lots of iTunes quirks remain, like the modal settings/preferences window that’s a holdover from the OS 9 days (OS X settings windows aren’t supposed to be modals).

My hunch is that they’ve got an actual from-scratch rewrite in the works that’s similar to the all-new WinUI-based Windows version of Music that came out a while back.

You could give my app a shot too:

https://www.plastaq.com/minimoon

The built in Finder sync is still very broken on my 5th Gen Video iPod. The most annoying breakage was trying to sync podcasts - it worked fine back when iTunes was the program to do that with, but when using the Finder sync on Big Sur it's buggy and does not remember your place in the podcast if you move to another track / podcast and back, which functionally makes podcasts longer than a few minutes unusable on the device.